Ring-tailed lemurs down by 95 percent? Maybe not.

A new paper claims that recent population estimates exaggerate the severity of ring-tailed lemur declines.

Article by Matthew P. Reed.

​

Conservationists are struggling to determine the status of Madagascar’s most iconic primate. A series of recent studies warning of sharp ring-tailed lemur (Lemur catta) declines stirred up a scientific debate over just how close to extinction the species really is. According to a paper published last month in the International Journal of Primatology, recent population estimates exaggerate the severity of ring-tailed lemur declines.

The new paper offers a rebuttal to two recent reports among several that outlined stark population declines for the famous lemur. Various news outlets, including Mongabay, covered the studies.

“[B]oth studies have likely severely underestimated the size of the extant ring-tailed lemur population because of a range of methodological problems,” the authors write, claiming that they suffer from misinterpretation of existing literature, incomplete sampling of lemur populations, and restricted geographic coverage.

Listed as Endangered on the IUCN Red List, the species is increasingly threatened by habitat destruction, illegal hunting, and illegal capture for the pet trade, among other factors.

​

Ring-tailed lemur. Photo by Rhett A. Butler.

​

For one of the studies, published last December in the journal Primate Conservation, researchers collected population information, from their own surveys and existing scientific literature, on 34 sites across the ring-tailed lemurs’ range. The authors conclude that only 2,000 to 2,400 of the animals remain in the wild.

In the other study, published in the journal Folia Primatologica in January, a separate team of researchers using similar methods collected population estimates from 32 sites across the ring-tailed lemurs’ range. The authors warn of a 95 percent population decline since the year 2000, and estimate that only 2,220 individuals remain at the sites surveyed in their study.

Both studies were disconcerting to conservationists because ring-tailed lemurs are known for their resiliency and adaptability.

So how many ring-tailed lemurs are actually left in the wild? The authors of the new rebuttal paper agree that there is ample evidence pointing to ring-tailed lemur population declines and local extinctions in recent decades. However, they firmly disagree with the notion that the species is on the verge of extinction.

“I agree that ring-tailed lemurs have faced overall population declines, just like many species in Madagascar have in the past few decades. But I don’t believe it is a ‘95% decline’,” lead author Asia Murphy, a PhD candidate in ecology at Pennsylvania State University, told Mongabay in an email.

Barry Ferguson, one of Murphy’s co-authors and an ecologist at Madagascar’s School of International Training, agreed that some population declines were likely. “Habitat clearance and degradation are evident causes. However, Lemur catta is extremely flexible, and in many cases lives in and very near human settlements, and feeds outside natural forests,” he told Mongabay.

Among a series of specific critiques, the rebuttal paper contends that both studies showing stark ring-tailed lemur declines inaccurately used limited data from previous research to make broad assumptions about large reserves and protected areas. In Tsimanampesotse National Park in Madagascar’s southeast, for example, Murphy pointed out that the authors of the Folia Primatologica paper used surveys from just two locations to represent the entire 2,000-square-kilometer (772-square-mile) reserve.

That study’s lead author, Marni LaFleur, a biological anthropologist at University of California San Diego and founder of the non-profit Lemur Love, defended her findings. “Our methods were clear and we repeatedly identify the possibility of both overestimates and underestimates,” LaFleur told Mongabay.

Another critique in the rebuttal paper is that the sites the two studies focus on “form an incomplete and potentially unrepresentative sample of known ring-tailed lemur populations.” For instance, it points out that the studies either did not account for at least 45 locations where ring-tailed lemurs have been observed in recent decades or wrongly included the locations as no longer having lemurs. This made both the geographic range and the total population of the species appear smaller than they really are, according to the paper.

The criticism came as somewhat of a surprise to the Primate Conservation paper’s authors. Lisa Gould, a primatologist at the University of Victoria, and Michelle Sauther, a biological anthropologist the University of Colorado, Boulder, have been studying ring-tailed lemurs since the 1980s.

In an email to Mongabay they explained that their dataset was limited to recent surveys conducted between 2000 and 2016, primarily because of the volatile situation plaguing wildlife in Madagascar. They acknowledged that precise population estimates would require accurate, current survey data, but argued that Murphy and her colleagues failed to present any convincing evidence to the contrary.

“[T]hey provide no actual population data in the table of 45 additional sites,” Gould and Sauther told Mongabay. “Their argument lacks the very aspect for which they criticize us — they provide no robust density estimates nor rigorous census methods.”

Gould and Sauther went on to contend that the rebuttal paper does not acknowledge the rapid loss of habitat occurring in Madagascar, even in areas once considered protected. They also noted that cultural taboos — known in Madagascar as fady — that once protected lemurs from illegal hunting have begun to erode with the influx of outsiders.

​

Family of ring-tailed lemurs. Photo by Rhett A. Butler.

​

Researchers from both sides of the debate agreed that a more complete estimate of ring-tailed lemur populations is needed.

Ferguson, co-author of the rebuttal paper, dismissed the possibility of scientists conducting traditional walking surveys. He argued that the remoteness and size of ring-tailed lemur habitat, coupled with the difficulty of detecting them given their speed and camouflaging coloration, make this method impractical. Instead he said the solution would involve working with on-the-ground conservation organizations to survey local people who know where the lemurs live.

“I am not an advocate of spending loads of money on scientists doing transect walks in ‘new forests’ to work out the population status. I would advocate for a bottom up approach, drawing off local knowledge and on the ground conservationists,” he said.

For their part, Gould and Sauther said they have been considering deploying conservation drones to collect data on ring-tailed lemur populations in hard to reach areas of the species’ range.

Some of the researchers on both sides of the ring-tailed lemur population question also agreed that it’s time to act to protect the species.

Yet even there, a difference of opinion emerged, with Ferguson arguing that more imperiled lemur species, such as the critically endangered blue-eyed black lemur (Eulemur flavifrons) or the critically endangered sportive lemur (Lepilemur septentrionalis), should take conservation priority.

“[Q]uite frankly with limited conservation funds available, I would personally allocate zero ‘lemur conservation money’ to Lemur catta right now, and focus on the species which are actually about to go extinct,” Ferguson said.